1. Field of the Invention
The present invention relates to a technique for optically observing an observation object site within a living body, and in particular, to a scattering medium internal observation apparatus, an image pickup system, an image pickup method and an endoscope apparatus for observing blood vessels, nerves and the like existing within a living body.
2. Description of the Related Art
When performing a surgical operation such as a removal of a diseased portion, the operation proceeds while being aware of positions of circulatory organs such as blood vessels and lymph channels as well as nerves in order to avoid damaging the same. During such an operation, a surgeon-in-charge must have intimate anatomical knowledge of positions of blood vessels and the like. In particular, it is essential that locations of blood vessels are identified.
However, the arrangement and distribution of blood vessels and the like vary between individuals. Accordingly, since it is required that an operation be performed while cautiously identifying the positions of blood vessels, surgeries tend to be prolonged.
A prolonged surgery leads to an increased burden on the patient. In order to reduce the burden to be borne by the patient, a method is required which enables positions of blood vessels and the like to be identified regardless of differences in the distribution of blood vessels and the like between individuals.
As a method for obtaining positional information on blood vessels, a vein authentication technique is disclosed in Japanese Patent Application Laid-Open Publication No. 2000-339445.
The disclosed vein authentication technique identifies individuals using differences in vascular arrangement and distribution which exist between individuals, and is applied to information security management as an alternative to personal identification numbers and passwords used for information management.
The vein authentication technique disclosed in Japanese Patent Application Laid-Open Publication No. 2000-339445 is a technique for detecting a vein existing in the vicinity of palmar skin using light absorption characteristics of blood hemoglobin. A palm is irradiated with a light having a wavelength band of 700 to 1000 nm for which blood hemoglobin has light absorption characteristics, whereby the arrangement and distribution of veins in the vicinity of skin are detected based on distribution information of differences in intensities of irradiated light and returned light.
In addition, there conventionally exists a method for observing an observation object site by reducing the influence of scattering by tissue in the vicinity of a living body surface when observing the inside from the surface or the influence of matter existing between an observation apparatus and the observation object site, as well as a method for observing an observation object site using pulsed light in an infrared wavelength.
For example, a technique disclosed in Japanese Patent Application Laid-Open Publication No. H06-022968 aims to reduce the influence of scattered light by synchronizing with a pulsed light generated by a light source and temporarily picking up an image transmitted from image transmitting means using instantaneous image pickup means.
Furthermore, a technique disclosed in Japanese Patent Application Laid-Open Publication No. 2005-261826 involves observing an observation object using a terahertz-range wavelength generated using an infrared pulsed laser.
Furthermore, in recent years, a device is proposed which is capable of obtaining, for example, the number of blood hemoglobin, a state of vascular flow, or the like as information regarding the inside of a living body tissue by irradiating the living body tissue with infrared light having a wavelength band that corresponds to light absorption characteristics of blood vessels, blood, and the like.
As a device capable of obtaining information regarding the inside of a living body tissue as described above, for example, there is a vascular visualization method proposed in Japanese Patent Application Laid-Open Publication No. 2004-237051.
The vascular visualization method proposed in Japanese Patent Application Laid-Open Publication No. 2004-237051 enables a state of vascular flow to be obtained as information regarding living body tissue existing at a desired observation site while removing, using a light-shielding apparatus, reflected light reflected off a surface of the living body tissue among reflected light of illuminating light having a predetermined band based on a hemoglobin-absorption spectrum and which is irradiated to the living body tissue, by receiving reflected light reflected after reaching blood vessels directly underneath the living body tissue with a CCD (charge coupled device).
Meanwhile, recently, in the field of medicine or the like, endoscope apparatuses using an endoscope have come to be widely used in examinations, observations, and treatment using a treatment instrument.
In addition, there are cases where an endoscope apparatus is used to observe a flow of blood vessels as an internal observation object tissue inside living body tissue within a body cavity. For example, a conventional example described in Japanese Patent No. 2528104 discloses an endoscope apparatus that brings a distal end face of a light guide into close contact with living body tissue in order to suppress reflected light from the living body surface.
Furthermore, Japanese Patent Application Laid-Open Publication No. 2005-192945 discloses a medical apparatus protruding in a cylindrical shape from a distal end portion of an insertion portion of an endoscope and which performs suction through ultrasonic vibration.